Field of the Invention
The invention relates to a filter configuration for vapor extraction hoods for the separation of particles and/or liquid droplets, which are used, in particular, in kitchens above a cooking are.
Filter configurations of this type are known. German Patent DE 27 20 201 C2 and U.S. Pat. No. 3,910,782 describe filters which are formed of a first row of profiles disposed at distances from one another and open in the direction of the gas flow and of a second row of profiles disposed at distances from one another and open opposite to the direction of the gas flow. The mutually adjacent longitudinal edges of two profiles of one row that lie next to one another projecting in each case into the inner space of an opposite profile of the other row.
In these separation grids, the distance between the two profile rows is dimensioned such that the air flowing through experiences a multiple reversal of direction. The free passage cross section amounts to 30% of the total grid area, depending on the separation grid—type 10. An increase in the air velocity of 3-10 times occurs within the separation grid due to the reduction in cross section. The separating action of the grid is based on this velocity increase, as a result of which the liquid droplets and solid particles contained in the air are of course also accelerated, and on the multiple reversal of direction of the air flowing through. The accelerated liquid droplets and solid particles cannot follow the direction change and impinge on to the inner surface of the profiles of the second row. On the surface of these, the liquid droplets form a liquid film that gradually runs off downward and passes through special orifices in the frame of the separation grid into a collecting rail disposed under the separation grid.
German Utility Model DE 298 11 000 Ul proposes a grease trap filter which makes use of two or more layers of a grid which are formed of slotted bridges produced on both sides of a metal sheet by a stamping operation, the grids being disposed within the filter in such a way that the slotted bridges run vertically or obliquely downward and the grids are held together by a common frame. A further grid, the slotted bridges of which are disposed horizontally, may be located in each case between two grids having slotted bridges running vertically or obliquely downward.
Furthermore, grease filters formed of multilayer expanded metal are known. Thus, Published, Non-Prosecuted German Patent Application DE 197 53 687 A1 describes a multilayer conically configured expanded-metal filter which has on the outside an integrally formed planar circular disk ring for good bearing against the filter frame.
An essential disadvantage of these plate-shaped or conically configured grease filters, in which the air, usually sucked in by a blower, flows through the plate plane, is the reduced edge suction extraction.
In order to eliminate this disadvantage, it has already been proposed in Published, Non-Prosecuted German Patent Application DE 41 38 846 A1, in a filter cartridge, via the filter surface of which the air to be filtered is sucked in, to divide the filter surface into subregions through which air flows and which inhibit the through flow. In this case, for the purpose of improved edge suction extraction, there is provision for the subregions which inhibit the through flow, to increase toward the center of the filter surface. This has the disadvantage, of course, that the overall filter surface is restricted in favor of flow optimization.
Furthermore, transverse-through flow plate-shaped separators for separating liquids from a gas stream, in particular an oil mist, are known from the industrial sector, and in these vortex elements, what are known as X-shaped vortex elements, are used, which bring about a deflection of the gas stream and consequently liquid separation (see German Patent DE 41 31 988 C2). Transverse-through flow plate-shaped separators of this type are not suitable for use in commercial kitchens or in domestic vapor extraction hoods.